Various styles of power driven meat cutting tools have been devised wherein a ring blade is rotatably mounted on a blade holder which in turn is mounted on a manually operated, power driven handle or handpiece. These tools have been used for some time in the meat industry to facilitate the removal of meat from a carcass primarily in a trimming operation or for removing the meat remains from the bones. These meat cutting tools are either electrically driven or pneumatically driven. An example of a pneumatic driven tool is shown in U.S. Pat. No. 3,852,882. Examples of electric meat cutting tools are shown in U.S. Pat. Nos. 3,024,532; 3,269,010; 4,494,311; 4,363,170 and 4,575,938.
These electrically driven tools generally consist of a tubular handpiece formed of metal or a synthetic plastic material having a hollow bore. An annular blade holder is attached to the front portion of the handpiece with a ring-shaped cutting blade being removably mounted thereon by various mounting arrangements. The blade is formed with gear teeth extending about the top thereof, which teeth are in driving engagement with a pinion gear mounted within the front end of the handpiece. A flexible drive cable is connected at one end to the pinion gear for rotating the ring gear with the other end of the cable being connected to an electric motor located adjacent to an operator work station, generally at a position overhead from the operator. The flexible cable extends from the electric motor to the handpiece and provides the power for rotating the cutting blade. The cable terminates in a squared end which is engaged in a complementary opening in the rear of the pinion gear for rotatably driving the gear.
An operator will start and stop the rotation of the cutting blade by actuating the main switch on the electric drive motor mounted overhead of the work station. This necessitates the operator reaching overhead each time he wishes to start and stop the electric drive motor, and consequently the cutting blade. Therefore, due to the amount of motion that must be performed by the operator to start and stop the trimming knife, the operator usually will permit the main electric motor and knife blade to continue to run between brief pauses in the trimming of the meat from different carcasses which may be brought to the work station on a conveyor or passed to the operator from an adjacent operator. This requires the operator to continually maintain his grip on the handle of the trimming knife with sufficient pressure to prevent the handpiece from twisting or turning in the hand. This continuous pressure over extended periods of time or throughout a usual work shift, fatigues the operator which then decreases the amount of production or meat trimmed during a work shift. Also the handles of the trimming knives usually become coated with grease from the fat of the meat being trimmed requiring sufficient pressure to be maintained on the handle to prevent the handle from turning in the operator's hand due to the rotational motion applied on the handle by the energy of the rotating blade.
Preferably an electric switch is not mounted on the handpiece itself for controlling the overhead electric motor due to the safety involved since the handpiece is usually used in a wet environment and must be cleaned during and after each work shift for sanitary reasons. Therefore, it is impractical to have an electric control switch on the handpiece itself which would permit an operator to conveniently stop and start the drive motor during momentary work stoppages during a work shift.
It is also important that when starting the drive motor that the operator either have at least one hand on the handpiece with the other hand being at a sufficient distance from the handpiece to prevent accidental cutting upon starting the drive motor, or have both hands on the handpiece.
Another problem with prior art electric driven knives having a usual manually actuated ON/OFF switch on the overhead electric motor is that the continuous running of the motor and handpiece blade throughout much of a work shift increases the maintenance cost of the knife. Also the cutting blade, the blade housing, drive pinion gear and flexible drive cable and casing therefor will require replacement more often throughout the operating life of the trimming knife if the blade is continuously rotated even when not in use by the operator.
Another problem with prior art electrically driven knives, is that due to the various sizes of handpieces required for various trimming operations, usually two different sized electric drive motors for the flexible drive cable are required to provide sufficient torque at the cutting blade to perform the required trimming procedure without excessively stalling of the blade and without providing too large a torque to the cutting blade. This required that the manufacturer provide at least two separate sizes of electric drive motors, associated housing and controls for the various handpieces, as well as requiring the user of the handpieces to stock additional inventory of motors and parts, since most trimming operations require various sizes of the handpieces.
Therefore, the need has existed for an improved control system for stopping and starting the rotation of the cutting blade of a meat trimming knife in a simple, economical, efficient and safe manner; and for a mechanism to easily change the torque supplied to the flexible drive cable by the electric drive motor.